Why don't you uninstall it and then install it again.... put FF 3.6 in which is out now.

Follow this Mozilla tutorial to uninstall...you have the option to keep or remove your settings. Try keeping them first and if that does not work repeat the process from the beginning again by removing the settings (profiles) folder as shown....remove the Profiles Folder as instructed any way if you are not bothered. It is possible to copy and paste the Profiles folder to your Desktop. Documents to play with later.